Hello,
This is only my first post and I am pretty new to the hardware side of design.
I was wondering how I would go about receiving a specific radio wave frequency then storing it and re-broadcasting that exact same frequency?
Hopefully someone can enlighten me! :
Many Thanks! ;D
Some specific frequency you have in mind?
Any really, I had a few ideas last night which come to something...
If I were to have and antenna (for receiving the signal) which would then be connected to a 'crystal oscillator' which would be set to a specific frequency (or could be variable using a variable capacitor), then this output would go into an analog-to-digital converter which the 'arduino' could understand and store. Then to re-broadcast it the 'arduino' would simply pass the same signal through a digital-to-analog converter which would then go through the oscillator and finally out via the antenna.
Does that sound like rubbish or is my GCSE physics paying off?
This scenario has been getting at me for some time....
Cheers
Does that sound like rubbish or is my GCSE physics paying off?
Better ask for a refund 
You need to relearn the basics of RF communications before even attempting to try and interface to an Arduino board. RF and digital are almost two different worlds and only recently has direct RF comm usable in the digital world via DSP (digital signal processing) using very high speed A/D and D/A.
It can be done, direct receiving and sending of RF, but not with a typical 8 bit AVR processor. Also storing (recording) any stream of information is also something the Arduino platform is not really good at as it's limited with the size of it's data memory and external storage modules/components would be required.
Your best bet is to search out ham radio sites that have RF fundamentals, projects, and possibly DSP information.
Good luck;
Lefty
WA6TKD
Okay, am I right in saying that I could pick-up a certain radio frequency by using a crystal oscillator to generate a matching sine wave?
How would I then go about "recording" this data without actually bothering with demodulation etc. then converting this data back and re-broadcasting it through the crystal oscillator and the antenna?
This sounded simple in my head I know...
Cheers.
Okay, am I right in saying that I could pick-up a certain radio frequency by using a crystal oscillator to generate a matching sine wave?
No, a oscillator generates a RF sine wave, it does not receive or detect RF signals.
How would I then go about "recording" this data without actually bothering with demodulation etc. then converting this data back and re-broadcasting it through the crystal oscillator and the antenna?
Not possible, you are missing many steps and stages and a crystal oscillator would only be able to send a sine wave output, not a modulated RF signal without additonal stages and circuitry.
This sounded simple in my head I know...
Fix the head, insert new knowlege.
Lefty
or is my GCSE physics paying off?
That implies that you are in the UK. If so what you are trying to do is illegal at any frequency without a licence. The only licence you can get to build your own transmitters is the Radio Amateurs Licence, see:-
Not sure what you are trying to do anyway but transmitting and receiving on the same frequency has limited applications.
As lefty says it is not just the carrier that carries the information unless you are talking about CW modulation, that's called Morse code in layman's speak. There are many ways to modulate an RF signal, AM, FM, PM & SSB are just four of the simpler methods. A circuit will only normally demodulate one method so you have to firm up on your ideas.
So the iTrip's and FM transmitters that I and thousands of others have in our cars are illegal?
Yes I understand about the different types of modulation, I was talking about recording the radio wave as it is, so as not to modulate/demodulate the sine wave.
Regards.
So the iTrip's and FM transmitters that I and thousands of others have in our cars are illegal?
Until very recently (late 2006), yes they were in the UK, even though they were openly on sale.
They always had a "not legal to operate in the UK" sticker on them, which everyone ignored.
May still be illegal in other parts of Europe.
Their maximum range is very strictly limited.
It is unclear what it is you hope to achieve, but your iTrip operates in the range 88-108MHz.
Your Arduino operates at 16MHz, and can digitise only at a few tens of kHz, way below even long or medium wave frequencies.
Would I not be able to use the arduino to produce a frequency at 423.75 kHz then? If not are there any components which I could use to help me with this?
Many Thanks.
Would I not be able to use the arduino to produce a frequency at 423.75 kHz then?
16MHz / 423.75kHz = 37.75 instruction cycles.
Feasible, but inexact.
RFID?
FM transmitters that I and thousands of others have in our cars are illegal?
Exactly what AWOL said - also while you can now operate a transmitter in this band it has to be a "type approved" transmitter. That is the design has to be certified and tested before it is legal to operate it. If you made your own iPod transmitter it would be illegal to operate it.
What you are thinking of doing is called direct synthesis of an RF signal and is something I am working on for my paid job, only we are doing it for digital TV signals. However, as pointed out the arduino is not fast enough for this. Nor does it have enough memory to store more than a cycle of RF even at these low frequencies.
If you say what you want to do then maybe there is a way to achieve what you want to do some other way but exactly what you are asking for is way out of the league of the sort of processor in an arduino.
There are other options like SPI controlled waveform generators that could help you but I don't know what you want to do. Also the LTC6904 might be worth looking at. These generate square waves but at these sorts of frequencies they can be easily filtered.